The goal of this research is to establish cultures of human medullary carcinoma and study the molecular forms of calcitonin produced and the regulation of this process. Since this research has been active for only 2 months, the progress has been limited. Several different calcitonin-producing cultures derived from human medullary carcinoma of the thyroid (MCT) have been carried for 6 months. The appearance of the cells and the relatively high calcitonin concentrations in the medium strongly indicate that one or more continuous tumor cell lines from MCT will be available for experiments in the very near future.